(a) Field of the Invention
The present invention relates to a roll forming device for forming a variable thickness plate. More particularly, the present invention relates to a roll forming device for forming a variable thickness plate in which an initial gap between an upper forming roll and a lower forming roll, which are disposed on a forming device, is set, and a spring unit absorbs a forming reaction force that is applied to the upper forming roll depending on a material thickness to be able to control a gap between the upper forming roll and the lower forming roll in real time.
(b) Description of the Related Art
Generally, forming of a line-type beam is performed by a roll forming system in which at least ten roll forming devices having an upper forming roll and a lower forming roll are disposed in line to bend and form supplied material into various shapes.
FIG. 1 shows a roll forming device of a general roll forming system and processes for each step.
Referring to FIG. 1, the roll forming system and process include an uncoiling step S110 in which an un-coiler 201 unfolding a supplied coil 200 is disposed at a front side of a process line, and a straightening step S120 in which a straightener 203 straightening a band-type coil 200 unrolled from the un-coiler 201 to a flat steel plate 250 is disposed at a rear side thereof.
Further, a brake press 205 is disposed at a rear side of the straightener 203 and performs a piercing step S130 to form various holes that are used to assemble a beam that is to be formed.
At least ten roll forming devices (207: R1-R7; partially not shown) are disposed at a rear side of the brake press 205 perform a roll forming step S140, which sequentially bends the steel plate 250 supplied through the un-coiler 201, the straightener 203, and the brake press 205, to a beam having a desired shape.
A round bender 209 that has a plurality of curvature forming rolls, which are disposed along a radius of a curvature for forming a curvature of a roll forming product, is disposed at a rear side of the roll forming device 207, and fabricates a predetermined curvature to perform a bending step S150.
However, in the conventional roll forming system, upper and lower forming rolls are is disposed at each roll forming device (R1-R7), and when a material is inserted, a gap deviation is formed between the upper forming roll and the lower forming roll by a forming reaction force, or particularly, in a case that a thickness of the material such as a TWB (Tailor Weld Blank) or a TRB (Tailor Rolled Blank) is changed, there is a drawback that a forming pressure exceeds a predetermined range by a predetermined gap between the upper forming roll and the lower forming roll.
Particularly, it is difficult to control a gap between an upper forming roll and a lower forming roll when plates (TWB, TRB, and so on) having different thicknesses in a length direction are inserted in real time, because it is difficult to accurately control a gap by using a servo motor in real time, so left and right forming deviations are generated on the upper forming roll and the lower forming roll, and thus there is a problem that a defective product is formed by a distortion that is caused by a forming pressure difference.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.